This invention pertains to computer systems and other information handling systems and, more particularly, to a computer system employing at least two fans in its cooling system and a movable baffle that, in the event of a failure of one of the fans, restricts the loss of air flow from the working fan out through the compartment housing the failed fan.
In many computer systems that use forced air cooling, multiple air moving devices are frequently used so that if one air moving device fails, the other can provide cooling for the system. If the computer system has a low air flow impedance and one of the air moving devices fails, then any leakage of air back through the failed air moving device is usually insignificant. In a computer system having a high air flow impedance, however, the failure of an air moving device usually causes the air flow from the working air moving device to leak out of the system through the failed device. This reduces the air flow through the system, thereby reducing the cooling of integrated circuits and other heat generating devices. This problem can be particularly acute when the air moving devices are arranged in parallel.
As microprocessors become more complex, they consume more electrical power and generate more heat, which must be removed. High density heat sinks are frequently used to cool processor modules, but these heat sinks offer a significant impedance to air flow. For example, an air flow of more than 20 CFM at 600 FPM is required to cool about 130 Watts of power generated by a processor module in a current, state-of-the-art, four processor computer system, and an air flow of 20 CFM though the heat sink can offer an impedance of more than 0.2 inch of water.
To achieve cooling redundancy in such a system, multiple air moving devices, such as blowers or fans, are typically installed in parallel and fully ducted through the processor modules first so as to provide sufficient quantities of air to cool the system when one of the air moving device fails. The high impedance of the processor module heat sinks causes the plenum in the computer system to become pressurized when the air moving devices are operating. When one of the air moving devices fails, the high air flow resistance (air pressure drop) through the processor module heat sinks will cause a significant amount of air from the functioning air moving device to leak out through the failed device, rather than cooling the processor modules. This reduction in air flow over the processor module heat sinks can significantly impact system cooling.
The prior art solution to this problem is to use gravity operated baffles, one over each outlet of the compartments that house the fans. Besides requiring one baffle per fan compartment, a disadvantage of this prior art solution is that the working fans must overcome the weight of the baffle in order to open up the air flow path, thereby adding impedance and decreasing cooling efficiency.
To overcome the problem of air leakage through a failed air moving device and the disadvantages of the prior art solution, the invention described below includes a movable baffle between two air moving devices that automatically and significantly increases the reverse air flow impedance through a failed air moving device, but without significantly increasing the forward air flow impedance through a functioning air moving device.